One known example of a mobile crane is one structured such that a fly jib is removably attached to a tip end of a boom for use, in order to expand the range of work that can be performed by the boom. The fly jib is stored on the boom in a state of extending along a side surface, lower surface, etc., of the boom, the boom being mounted on an upper turning body so that it can be raised and lowered.
When crane work is performed using a fly jib, the fly jib is attached in a state of extending frontward of the boom from a tip end part of the final-stage movable boom of the boom. Additionally, a raising/lowering rope for raising and lowering the fly jib, with the boom tip end part as a fulcrum, is stretched from the same side as the boom to the fly jib side, otherwise a fly jib raising/lowering cylinder is stretched between the boom and the fly jib.
Patent Document 1 proposes a mobile crane in which a fly jib is raised and lowered using a raising/lowering wire rope. Patent Document 2 proposes a jib raising/lowering device for a crane in which a fly jib is raised and lowered using a raising/lowering cylinder. In extracted work in which the fly jib is switched from a stored state to an extracted state, and also in storing work, a raising/lowering rope or a raising/lowering cylinder must be stretched between the boom and the fly jib, which is labor-intensive.
Various instruments are installed on the fly jib in order to detect an angle of inclination, an exerted load, length, a wound-up state of an auxiliary hook suspended from the fly jib, etc. Signal lines and power supply lines led out from the boom side are connected to the instruments installed on the fly jib. In the work of extracting/storing the fly jib, work must be performed to guide and connect/disconnect numerous wires, which is troublesome. Additionally, there are cases in which the numerous wires cannot be appropriately guided to the fly jib, which is smaller in cross-section than the boom. Furthermore, in the case of numerous cables, the cable diameter is greater and the reel is larger as well.
Patent Document 3 proposes a cable winding device that uses a multi-core conductive cable suitable for placement in a telescopic boom, which is an extendable/retractable multi-stage boom. Patent Document 4 proposes a communication system in which, in construction machinery, a driver-cabin-side control device and unit-side control devices disposed on the left and right of an upper turning body are connected by a CAN communication line. However, in the prior art, there has been no focus on efficiently performing the work of connecting/disconnecting the numerous signal lines and power supply lines stretched between the fly jib and the boom in the work of extracting/storing the fly jib.